Characterisation and bioactivities of an exopolysaccharide from an Antarctic bacterium Shewanella frigidimarina W32–2

Abstract

The continent of Antarctica breeds numerous special extremophiles that have adapted to the extreme variation of environment with a wide range of novel biodiversity. A cold-adapted bacterium Shewanella frigidimarina W32–2, isolated from Antarctic sediments, was identified to be a promising candidate of exopolysaccharides (EPS) production. In the present study, the physiochemistry and bioactivities of the EPS were investigated to promote its application in aquaculture. Physiological characterisation of this strain was firstly performed by means of combined API 20NE and API ZYM tests. A biochemical analysis revealed that the EPS contained a majority of carbohydrates (56.34 ± 1.29%), uronic acids (8.23 ± 0.55%) and high content of sulphate groups (35.43 ± 1.84%), which were also confirmed by the FTIR spectrum showing various functional groups with potential antioxidant activities. The bioactive properties of the EPS in vitro and in vivo were both evaluated. The effect of the EPS on the non-specific immunity of red tilapia via serum injection exhibited 100% of survival rate. Improvement of activities in different serum enzymes, including AKP, ACP, SOD, CAT and LZM, was observed generally at the early stage of EPS treatment (except LZM at later stage). This study explores novel EPS from an extremophile exhibiting powerful bioactivity with immense potential in aquaculture sustainability.